Rules of the Road

Maricopa County’s roadway network supports and encourages the movement of people and resources between destinations. To meet the needs of all roadway users, MCDOT relies on a combination of rules, regulations and public awareness to keep its roadways operating safely and efficiently.

Speed Limits

The Maricopa County Department of Transportation (MCDOT) is responsible for planning, designing, building, maintaining and operating the County’s roadway network. The Maricopa County Sheriff’s Office (MCSO) is responsible for enforcing the roadway regulations approved by the Board of Supervisors.

How speed limits are set

Speed limits are based on engineering studies. These studies are conducted by MCDOT’s Traffic Studies Branch and take into consideration many factors which affect the safety and operations of a roadway.

These factors include:

Roadway classification: A roadway may be classified as a local residential street, collector road or major arterial roadway.

Lanes and shoulders: The size of travel lanes and shoulders influences how vehicles and other roadway users utilize the roadway.

Alignment and sight distance: Dips, curves, vegetation and other factors can affect how far ahead or behind a driver or other roadway user can see.

Current vehicle operating speeds: Engineers will conduct a speed study to determine how fast drivers are currently driving on the road. This study will determine the 85th Percentile speed. This is the speed at which 85 percent of all vehicles travel at or below. Speed limits may be set at or below the 85th Percentile, depending on roadway conditions.

Reported crash history: Engineers will consider reported crashes on the roadway as well as what may have caused the crash, if known, and other safety factors.

In addition to these factors, MCDOT strictly adheres to the guidance issued in the Manual on Uniform Traffic Control Devices (MUTCD) for setting speed limits. The MUTCD is the national standard for signing on all highways. Sections 2B.13-16 address regulatory speed limits and Section 2C addresses advisory speed signs. School zone speed limit signs are discussed in Section 7B and work zone speed limits in Section 6C.

Placement of portable speed feedback signs

These signs use radar to detect the speed of oncoming traffic and display the approximate speed in real-time. This allows drivers to compare their current rate of speed with the posted speed limit and make adjustments as necessary.

Due to the limited number of signs available for use by MCDOT, these portable speed feedback signs are prioritized for use in construction work zones and speed study locations throughout unincorporated Maricopa County.

Speed humps and traffic calming measures

MCDOT utilizes traffic calming measures, including speed humps to address excessive cut-through traffic on local roads. Roadways must meet the criteria of Maricopa County’s Traffic Calming Ordinance (P-29) 29), which is confirmed through an engineering study and requires the support of residents, businesses and emergency responders in the area. Based on input from local emergency responders, MCDOT will not consider the installation of speed humps in the Sun City or Sun City West communities because they may increase emergency response times in situations where every minute counts.

The Maricopa County Traffic Calming ordinance allows for several types of traffic calming measures to be studied and, if found to be warranted, constructed. These measures include:

Chicane: A combination of raised curb and striping to narrow lane width and reduce speed through on a local road.

Choker: The narrowing on one side or both sides of a local road in such a manner as to reduce speed without impairing safe two-way traffic.

Diverter: A barrier type device that forces traffic to make only a left turn or right turn at an intersection. A diverter is normally used to control direction and flow of traffic in residential neighborhoods.

Speed hump/cushion: An asphalt hump, approximately 3.25 inches high and up to 12 feet in width running across the road. The raised hump encourages drivers to reduce speeds while driving over them.

Traffic circle: A type of circular intersection, used primarily in low volume residential neighborhoods in which traffic must travel in one direction around a small central island. This encourages drivers to reduce speed while driving through neighborhoods.

Residents living on a County local road with a posted speed limit of less than 35 may request MCDOT study the feasibility of placing traffic calming devices on their street.

To become eligible for traffic calming measures:

MCDOT’s study must determine the roadway has at least 1,100 vehicles per day and 85 percent of those vehicles are travel at speeds at or below 8 miles the posted speed limit. The roadway network is also evaluated to determine if feasible alternative routes are available.

Additionally, 80% of property owners whose property is adjacent to the roadway segment must agree to traffic calming plans.

Speed Enforcement

The Maricopa County Sheriff’s Office is responsible for enforcing speed limits. Questions regarding speed enforcement, including use of radar and cameras to enforce speed limits, should be directed to MCSO at (602) 876-1000.

Roadway Maintenance

The Maricopa County Department of Transportation (MCDOT) is responsible for preserving and maintaining the County’s transportation investment. This includes maintenance of roadways, medians and shoulders, bridges and culverts, guardrail, street signs and traffic signals.

MCDOT maintained roadways

The Road Information Tool Opens a New Window. informs residents if their street is maintained by MCDOT. Viewers may choose to add layers to show additional roadway details including roadway classification, municipal annexation and subdivision information. A user guide is available in the “About” section on the right side of the map program.

Preserving pavement

The effects of weather and traffic on a roadway can cause even the most well-designed and constructed roadway to deteriorate over time.

MCDOT maintains its paved roadway network through a Pavement Management Program which identifies preservation treatments needed to prolong the life of the road by sealing cracks and waterproofing surfaces.

These treatments include:

Crack Seal

Micro Seal

Preservative Seal

Slurry Seal

Chip Seal

Prior to performing pavement maintenance, residents will receive a color-coded notice informing them that pavement maintenance will be taking place and what they can expect.

More information about the different types of pavement preservation is available on our Pavement Page.

Traffic signal timing and operations

Traffic signal timing programs set the timing of red, yellow and green lights at a signalized intersection in a manner that allows the signal to keep traffic moving safely and efficiently.

Traffic signal operations, including timing, are based on engineering studies. These studies are conducted on a regular basis and consider traffic patterns, volumes and crash data to set timing patterns.

Traffic signal timing studies take many factors into consideration when setting a signal timing pattern for an individual intersection. These factors include:

Traffic patterns: Many intersections see periods of time in the morning and evening “rush” hours where traffic patterns may be different than at other times of the day.

Volume: The number of vehicles traveling in each direction will influence how much time a signal will give to any particular direction of travel.

Reported crash history: Engineers will consider reported crashes at the intersection as well as what may have caused the crash, if known, and other safety factors.

MCDOT uses three types of timing systems at it signalized intersections.

Free/Uncoordinated Operation: Vehicle demands dictates the amount of green time a movement receives. Each signalized intersections operates independently and no traffic signal synchronization is provided along roadways.

Coordinated Operation: Coordination patterns are developed by traffic engineers to platoon groups of vehicles through a series of signalized intersections to provide smooth flow and progression/signal synchronization along roadways in order to reduce travel times, number of stops and delay.

Adaptive Signal Control Operation: Advanced traffic signal system software along with vehicle detection systems are used to adjust green light durations, when the green light turns on, and the sequencing of the movements based on the demands in real-time while providing signal synchronization. The green duration and when the left-turn arrow comes up can be different each rotation keeping the motorist on their toes as the system adjusts the traffic signal timings in real-time based on movement demands. It is not unusual for a left-turn arrow to come up twice in one rotation.

MCDOT will review requests to evaluate a traffic signal’s timing patterns. Requests may be made through the “Contact Us” form.

Roadway drainage

MCDOT may utilize drainage structures including basins, channels, culverts and storm drains to remove water from roadways. The use of these structures is based on an engineering study which considers water source, natural flow and roadway operations. MCDOT only maintains drainage structures within its right of way to ensure they are free from debris and that water can flow freely.

Use of County Right-of-Way

The Maricopa County Department of Transportation (MCDOT) is responsible for planning, designing, building, maintaining and operating the County’s roadway network. This includes all work performed within the County’s right-of-way by third party contractors and property owners.

Signs in the right-of-way

Arizona State Law (ARS 16-1019) allows for the placement of temporary political signs in the right of way so long as the sign is not placed in a location that creates a hazard to public safety, obstructs clear vision or interferes with the requirements of the Americans with Disabilities Act (ADA).

Arizona State Law also prohibits the installation in the county right of way of any signs advertising the sale of an article, service or thing.

Driveway ramps

MCDOT does not permit the use of curb ramps or any other such device within County right of way. Curb ramps placed in MCDOT’s right of way are an unauthorized use of County right of way and are not allowed and must be removed. Homeowners who use these devices bear all responsibility and liability for their use.

Getting a permit

MCDOT requires a permit for any activity to occupy, use or construct improvements within County right-of-way. This ensures new improvements are built to County standards and that the safety requirements are met.